While not quite default XML format, so the default "Apply JSON Transformation" does not apply.
So need to code a custom answer for it.
The Gateway Policy is attached.
Here is an explaination of the code.
We set our variable as the JSON array with values :
Then evaluate JSON Path Expression, which returns an array of results :
Then we loop through the array building up the XML structure :
And to test it we fire off a request :
And get the response in the XML (or other) format we wanted: